This invention relates to drive apparatus for an irrigation line, and more particularly, to a drive apparatus including governor means for providing proper driving of the irrigation line over uneven terrain.
In, for example, a rotary-type irrigation system, an elongated irrigation line is supported at intervals by towers on wheels and water is supplied from the irrigation line to individual water motors associated with the towers to drive them over the ground, the entire irrigation line rotating about a central pivot axis. Generally, the outermost tower is provided with a valve so as to supply water of a certain pressure to the outermost drive motor, and means are included adjacent each tower for providing proper operation of each other water motor so that the irrigation line stays substantially in alignment as it rotates. With constant water pressure being applied to the outermost water motor, the entire irrigation line will be transported at a substantially constant speed over level ground. However, as the line is driven up a grade, the torque applied to the outermost water motor remains the same but with the necessity of such torque not only driving that portion of the irrigation line over the ground, but actually lifting it up the grade. Likewise, as the line is driven down a grade, the torque applied to the outermost water motor remains the same.
It will be understood that the overall speed of the outermost tower, and thus, the overall rotative speed of the irrigation line, changes substantially during either of these conditions. Yet the overall amount of water flowing from the irrigation line to irrigate the ground remains constant for a given period of time. This is a highly undesirable state since it will be seen that the uphill ground will be much more heavily irrigated, and downhill ground will be much more lightly irrigated than level ground being irrigated, when it is to be understood that substantially constant and even irrigation throughout the entire rotative cycle of the irrigation line is highly desirable.